Context: Sex hormones play a key role in women's health, but little is known about lifestyle factors that influence their levels.
Objective: The objective of the study was to investigate the relationship between cigarette smoking habits and endogenous sex hormone levels in postmenopausal women.
Design and participants: This was a cross-sectional study among 2030 postmenopausal women aged 55-81 yr from the Norfolk population of the European Prospective Investigation into Cancer. All women were at least 1 yr postmenopausal and not currently using hormone replacement therapy. General linear models were used to examine the relationship between smoking habits and sex hormone levels.
Results: Among current smokers, the daily number of cigarettes smoked was associated with increased levels of testosterone (19-37%), free testosterone (19-34%), 17-hydroxprogesterone (17-22%), androstenedione (2-23%), SHBG (6-10%), and estradiol (-2 to 15%). Stratified analysis for body mass index revealed an interaction such that the association with SHBG was restricted to lean women, whereas a smoking-related increase in free estradiol was found only in overweight women. No clear dose-response relationship was observed for estrone, although its levels were highest in heavy smokers. Current smoking habit was associated with a larger difference in sex hormone levels than lifetime cigarette exposure as measured by pack-years. Among former smokers, sex hormones were at levels of never smokers within 1-2 yr of smoking cessation.
Conclusions: Cigarette smoking is associated with higher circulating levels of androgens, estrogens, 17-hydroxprogesterone, and SHBG in postmenopausal women. The almost immediate lower levels with smoking cessation may indicate that hormone related disease risks could potentially be modified by changing smoking habits.